从Oracle9i开始,Oracle引入了自动PGA管理的新特型,PGA_AGGREGATE_TARGET参数用于控制PGA的总体期望目标:

$ sqlplus "/ as sysdba"

SQL*Plus: Release 9.2.0.4.0 - ProdUCtion on Thu Apr 6 16:40:13 2006

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

SQL> show parameter pga

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
pga_aggregate_target                 big integer 1073741824
SQL> 

    但是在Oracle9i中，PGA_AGGREGATE_TARGET参数仅对专用服务器模式下（Dedicated Server）的专属连接有效，对共享服务器（Shared Server）连接无效；从Oracle10g开始PGA_AGGREGATE_TARGET对专用服务器连接和共享服务器连接同时生效。

原文地址：http://www.eygle.com/archives/2006/04/pga_aggregate_target_changed.Html

（出处：网侠）